BuiltinRules override other rules in some cases.

It seems that the Class op * rules will override a user defined rule for class functions.

This seems to be a long outstanding issue: http://stackoverflow.com/questions/9811294/rewrite-rules-not-firing-for-rules-matching-multiple-instance-methods

I also just ran into someone else on the haskell IRC channel who had an even simpler example then the one on that page:

{-# NOINLINE d #-}
{-# RULES "d exp" d exp = exp #-}
d :: (Double -> Double) -> (Double -> Double)
d f = f . (+20.0)

g :: Double -> Double
g = (+5.0)

main = do
  print $ d exp 1.0     -- FAIL should print 2.718281828459045  >>  printed exp 21.0 instead
  print $ d g 3.0       -- PASS should print 28.0

-- Compiled with:
--   ghc -fenable-rewrite-rules -O rules.hs

Trac metadata

Trac field	Value
Version	7.10.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	high
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture